Packet-based communication systems allow the user of a device, such as a personal computer, to communicate across a computer network such as the Internet. Packet-based communication systems include voice over internet protocol (“VoIP”) communication systems. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long-distance communication. To use a VoIP system, the user must install and execute client software on their device. The client software provides the VoIP connections as well as other functions such as registration and authentication. In addition to voice communication, the client may also provide further features such as video calling, instant messaging, voicemail and file transfer.
One type of packet-based communication system uses a peer to peer topology built on proprietary protocols. To enable access to a peer to peer system, the user must execute peer to peer client software provided by a peer to peer software provider on their computer, and register with the peer to peer system. When the user registers with the peer to peer system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the peer to peer system without the further use of a server. In particular, the users can establish their own communication routes through the peer to peer system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the peer to peer system. The exchange of the digital certificates between users provides proof of the users' identities and that they are suitably authorised and authenticated in the peer to peer system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a peer to peer system are disclosed in WO 2005/009019.
It is known to connect more than two terminals via a communication system in a group call. In a group call, otherwise known as a conference call, a group of participating terminals may be connected together via a host terminal. The host is arranged to collect incoming signals from each participant terminal and combine the signals before sending the combined signals to the participating terminals.
Reference is made to FIG. 1 which shows a group of terminals 104, 114 and 124. The terminals are connected to the internet (not shown). Each terminal is operated by a user. In this case User A operates terminal 104, user B operates terminal 114 and User C operates terminal 124.
As shown in FIG. 1, User B may attempt to initiate a call with User A by transmitting a call set up request, CR, to User A when User A is engaged on a call with User C. User A is notified of the incoming call from User B and is provided with an option of authorising User B to be added to a group call with User A and User C.
One problem with this method is that the User A does not know whether User B wishes to be added to the group call.
Another problem with this method is that User A does not know if User C will object to the other user being added to the call.